Pyrolysis product of N-substituted-1-cyclohexene-1,2-dicarboximides

ABSTRACT

Pyrolysis of N-substituted-1-cyclohexene-1,2-dicarboximide gives N,N&#39;-substituted-pyromellitdiimides. Pyrolysis of N-substituted-1-cyclohexene-1,2-dicarboximide in the presence of N-substituted maleimides produces N,N&#39;-substituted-3,4,5,6-tetrahydropyromellitdiimide and the Diels-Alder dimer of N-substituted-1,3-butadiene-2,3-dicarboximide.

This is a Divisional application of Ser. No. 603,221, filed August 8,1975 now U.S. Pat. No. 4,056,542, patented Nov. 1, 1977; which is aDivisional application of Ser. No. 360,962, filed May 16, 1973, now U.S.Pat. No. 3,932,457, patented Jan. 13, 1976.

FIELD OF THE INVENTION

The invention relates to the production of pyromellitdiimides. Inanother aspect, the invention relates to tetrahydropyromellitdiimidesand methods to produce same. In a further aspect, the invention relatesto the dimer of N-substituted-1,3-butadiene-2,3-dicarboximide andmethods to produce same.

BACKGROUND OF THE INVENTION

In the field of polymer chemistry, the search continues for newcompounds suitable as monomers for the preparation of polymers usefulfor a variety of purposes. New routes to known monomers also arevaluable in providing alternative methods of producing valuablemonomers, such as pyromellitic anhydride which is particularly useful inproducing thermally stable heterocyclic polymers such as described in 16Encycl. Chem. Tech., 42 (1968).

OBJECTS OF THE INVENTION

It is an object of the invention to provide new compositions of matteruseful as monomers in the formation of polymeric products.

Another object of the invention is the provision for new routes touseful monomers.

Other aspects, objects, and advantages of the present invention willbecome apparent from a study of the dislcosure, and the appended claims.

DESCRIPTION OF THE INVENTION

I have discovered that the pyrolysis ofN-substituted-1-cyclohexene-1,2-dicarboximide (A) results inN,N'-substituted-pyromellitdiimide (B) and the dimer ofN-substituted-1-3,-butadiene-2,3-dicarboximide (C). TheN,N'-substituted-pyromellitdiimide (B) can be hydrolyzed, if desired, topyromellitic anhydride which is particularly useful in making thermallystable heterocyclic polymers.

I have further discovered that the pyrolysis ofN-substituted-1-cyclohexene-1,2-dicarboximide (A) in the presence ofN-substituted maleimide (D) yields the Diels-Alder dimer ofN-substituted-1,3-butadiene-2,3-dicarboximide (C) andN,N'-substituted-3,4,5,6-tetrahydropyromellitdiimide (E). The material(E) can be readily dehydrogenated to yield the aforesaidN,N'-substituted-pyromellitdiimide (B) which latter, if desired, can besubjected to the aforesaid hydrolysis to the corresponding pyromelliticanhydride. Or, the N,N'-substituted-3,4,5,6-tetrahydropyromellitdiimide(E) can be reacted with an alpha,omega-diamine to produce spongy,rubbery, solids. The Diels-Alder dimer ofN-substituted-1,3-butadiene-2,3-dicarboximide (C) can also be reactedwith alpha,omega-hydrocarbon diamines to produce polymeric productssuitable for a variety of applications, such as drying oils or corrosioninhibitors.

While I do not wish to be bound by theoretical considerations of howthese products are produced or in just what fashion the initialreactants form my novelN,N'-substituted-3,4,5,6-tetrahydropyromellitdiimide (E) and Diels-Alderdimer of N-substituted-1,3,-butadiene-2,3-dicarboximide (C),nevertheless, the following representations may assist in understandingthe novel reactions and the products I have discovered: ##STR1##

The compounds (C) and (E) may arise, respectively, by the reaction ofN-substituted-1,3-butadiene-2,3-dicarboximide (F) with itself or withN-substituted maleimide (D). The formation of the novel compounds (C)and (E) may be visualized as follows: ##STR2##

The postulated reactive intermediateN-substituted-1,3,-butadiene-2,3-dicarboximide (F) could be generatedfrom (A) as shown below: ##STR3##

In the above formulae, R can be phenyl or primary alkyl radical,preferably of 1 to 6 carbon atoms. While, in general, the R groups in(A) and (D) are the same, this is not necessary to the reaction, suchthat where more than one R group appears in a particular compound, or indiffering reactants, the R groups can be but are not necessarily thesame.

REACTION CONDITIONS

In accordance with my invention, the pyrolysis conversion reaction whichI have discovered is conducted under conditions of temperature andpressure sufficient to effectuate the pyrolysis conversion. The reactioncan be conducted at suitable elevated temperature and low pressuressufficient to effect the reaction desired. Contact times normally arerelatively short, to avoid undue loss or decomposition of reactants,intermediates, and end products. Presently preferred are reactiontemperatures in the range of about 500° to 1000° C., presently morepreferred in the range of about 700° C. to 800° C. Contacting pressurespreferably should be relatively low, such as 0.001 to about 100 mmmercury absolute, presently preferred about 1 to 50 mm mercury absolute.Contact times preferably are short, such as in the range of about 0.001to 1 second, preferably about 0.005 to 0.1 seconds, though some variancecan be practiced.

In effecting the pyrolysis reaction, treating the reactants in themolten condition at the specified temperatures and pressures for veryshort contacting times is one suitable mode. Treatment can be in areactor of quartz, or ceramic lined metal reactors such as a ceramiclined titanium autoclave and the effluent from the reactor preferably iscollected in a trap at dry ice temperatures, and can be purified such asby recrystallization or preparative gas chromatographic techniques.

While contacting can be and preferably is in the absence of a solvent,solvents are employable where desired or convenient to assist inhandling of some of the reactants, and solvents such as the alkyl arylcarboxylates such as methyl benzoate, or various pyridine compounds, ordialkylphthalates, such as dimethyl phthalate, aryl ethers such asdiphenyl ether, or other compounds such as benzonitrile, which arerelatively inert under the reaction conditions described, can beemployed in the process.

EXAMPLES

The examples provided are intended to assist and further illustrate thescope of my invention, and to assist in the understanding thereof.Specific reactions, specific reaction conditions, methods of handlingreactions, all should be considered as illustrative and not aslimitative of the reasonable scope of my invention as disclosed in thisspecification including claims.

EXAMPLE I

A charge of 5 g (0.045 mole) N-methylmaleimide and 5 g (0.03 mole)N-methyl-1-cyclohexene-1,2-dicarboximide in 25 g dimethyl phthalate assolvent was passed through a tubular reactor bed of quartz chips at 750°C. and 2.5 mm Hg over a period of 43 minutes using a 50 cc/min purge ofN₂ to facilitate the passage of the reactants through the reaction zone.The reactor effluent collected in cold traps amounted to approximately31.5 g. The reactor effluent collected was poured slowly into 600 mlether with swirling and a precipitate formed. This precipitate wasremoved by filtration and recrystallized twice from tetrahydrofuran. Thesolid product (m.p. 200°-203° C.) was shown to beN,N'-dimethyl-3,4,5,6-tetrahydropyromellitdiimide by elemental and massspectral analyses. Elemental analysis calculated for C₁₂ H₁₂ N₂ O₄ : %C, 58.09; % H, 4.90; % N, 12.05; Found: % C 58.08; % H, 4.90; % N,12.05. The molecular weight by mass spectral analysis was found to be248 (calculated mol. wt. 248) and the mass cracking pattern indicatedthe product to be N,N'-dimethyl-3,4,5,6-tetrahydropyromellitdiimide.

EXAMPLE II

A charge of 10 g (0.09 mole) N-methylmaleimide and 2.5 g (0.015 mole)N-methyl-1-cyclohexene-1,2-dicarboximide in 7.5 g pyridine reactiondiluent containing 0.1 g dimethyl phthalate (glc internal standard) waspassed through a tubular reactor bed of quartz chips at 750° C. and 10mm Hg over a period of 19 minutes using a nitrogen purge. The reactoreffluent collected in cold traps amounted to approximately 17.2 g. A glcanalysis of the reactor effluent showed the presence of

N,n'-dimethyl-3,4,5,6-tetrahydropyromellitdiimide and the dimer ofN-methyl-1,3-2,3-dicarboximide. The glc analysis showed 49.8 area % ofN,N'-dimethyl-3,4,5,6-tetrahydropyromellitdiimide and 43.8 area % of thedimer of N-methyl-1,3-butadiene-2,3-dicarboximide. Retention times wereutilized to verify the presence ofN,N'-dimethyl-3,4,5,6-tetrahydropyromellitdiimide and the dimer ofN-methyl-1,3-butadiene-2,3-dicarboximide. The sample ofN,N'-dimethyl-3,4,5,6-tetrahydropyromellitdiimide used for this purposewas prepared in Example I. The sample of the dimer ofN-methyl-1,3-butadiene-2,3-dicarboximide used for this purpose had amelting point of 139°-140° C. and its structure was verified byelemental, mass spectral and nuclear magnetic resonance analyses:

a. Elemental analysis for the dimer ofN-methyl-1,3-butadiene-2,3-dicarboximide C₁₄ H₁₄ N₂ O₄ : Calc'd % C,61.3; % H, 5.1; % N, 10.2; Found: % C, 61.46; % H, 5.27; % N, 10.93

b. Mass Spectral Analysis for the dimer ofN-methyl-1,3-butadiene-2,3-dicarboximide: Mol. wt. 274 (Calc'd 274)

c. ¹³ C Nuclear Magnetic Resonance data supported the structure of thedimer of N-methyl-1,3-butadiene-2,3-dicarboximide as shown above byexhibiting resonances specifically from:

3 methylene units

1 quaternary carbon

3 olefinic carbons with no protons attached

1 olefinic carbon with two protons attached

2 methyl groups

3 types of carbonyl groups

EXAMPLE III

A 9.8 g (0.06 mole) molten sample ofN-methyl-1-cyclohexene-1,2-dicarboximide was passed through a tubularreactor bed of quartz chips at 700° C. and about 20 mm Hg over a periodof ten minutes using a nitrogen purge. The reactor effluent wascollected in a mixture of methanol/tetrahydrofuran and stored at dry icetemperature. The precipitate which formed was removed by filtration andrecrystallized three times from tetrahydrofuran to give a solid whichmelted at 375°-378° C. in a sealed tube. The solid sublimed at 350°-360°C. in an open tube. This product was shown to beN,N'-dimethylpyromellitdiimide by elemental, infrared and mass spectralanalyses.

EXAMPLE IV

A 0.49 g (0.002 mole) sample ofN,N'-dimethyl-3,4,5,6-tetrahydropyromellitdiimide was mixed with 0.29 g(0.002 mole) 1,8-octanediamine and the mixture heated to and maintainedat 195° C. for three hours. During the reaction period the mixturebecame blue-green in color and a gas was evolved. The mixture becameviscous and by the end of the reaction period a spongy rubbery polymericproduct was formed which was insoluble in tetrahydrofuran.

EXAMPLE V

A 1.61 g (0.0059 mole) sample of the dimer ofN-methyl-1,3-butadiene-2,3-dicarboximide was mixed with 0.85 g (0.0059mole) 1,8-octanediamine and the mixture heated to and maintained at 195°C. for three hours. During the reaction period, a blue-green colordeveloped and a gas was evolved. The viscous liquid product wascompletely soluble in tetrahydrofuran.

The N,N'-substituted-3,4,5,6-tetrahydropyromellitdiimide compounds of mydiscovery can be reacted as demonstrated with α,ω-diamines to producespongy rubbery solids which can be employed for tire cords or moldingresins. These N,N'-substituted-3,4,5,6-tetrahydropyromellitdiimides canbe readily dehydrogenated in the presence of metals such as palladium,platinum, ruthenium and the like, or by thermal treatment with sulfur toproduce the corresponding N,N'-substituted-pyromellitdiimides. Asdescribed in 72 Chem. Abstr. 66629e (1970), the latter compounds can bereadily separated and converted, by hydrolysis, to pyromelliticanhydride. Pyromellitic anhydride is known for making thermally stableheterocyclic polymers such as described in 16 Encycl. Chem. Teach. 42(1968).

Other modifications and alterations of this invention will becomeapparent to those skilled in the art from the foregoing discussion andaccompanying drawing, and it should be understood that this invention isnot to be unduly limited thereto.

I claim:
 1. The Diels-Alder dimer ofN-phenyl-1,3-butadiene-2,3-dicarboximide.
 2. The Diels-Alder dimer ofN-alkyl-1,3-butadiene-2,3-dicarboximide.
 3. The Diels-Alder dimer ofN-alkyl-1,3-butadiene-2,3-dicarboximide of claim 2 wherein said alkyl ismethyl.